7-Chloro-5-(2-chlorophenyl)-1,3-dihydro-2H-1,4-benzodiazepin-2-one is a compound of the formula: ##STR2##
This compound (I) has been known by its chemical structure for many years but it has been studied pharmacologically and clinically in depth only recently and these studies have shown that it possesses an activity far exceeding that of the best known benzodiazepines already commercially available.
This has given rise to a need for finding an industrial process by which this compound can be produced in pharmaceutical purity in an economically acceptable manner.
It is known from British Pat. No. 1,063,891 that a limited group of benzodiazepinones comprising in particular a phenyl group non-substituted in position 5, can be prepared by hydrazinolysis of a phthalimidoacetamide of the formula: ##STR3## in which R.sub.1 is hydrogen, methyl or ethyl; R.sub.2 is halogen and R.sub.3 is hydrogen, alkyl, phenyl or p-hydroxybenzyl.